Estes Saturn V Skylab centering rings?

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I’m finally getting around to building the kit I purchased over year ago. The recommended engines are E16 and F15. I’m thinking of upgrading the engine mount to handle G engines which will require cutting the 100mm tube somewhere above above the height of the engines to insert an extra centering ring and to provide access for securely glueing the CRs to the tubes. I’ll need to provide a tube coupler here also. Hopefully this main tube splice can occur under the second wrap from the bottom to hide it.
In checking out the parts supplied I found the centering rings supplied for the engine mount tube were extremely loose-fitting in the 100mm tube. They basically fell thru the tube. Don’t know how anyone could secure these properly to the tube to take the stress of an E or F engine. I constructed new centering rings and they were almost 2mm larger in diameter than the kit supplied ones.
Just wondering if others found these CRs to be loose-fitting.
 

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cls

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I think they are supposed to be loose. The Saturn V instructions say not to glue the upper ring, because the contracting glue would dimple the airframe.

I haven't looked at my Skylab kit but I bet it's the same.
 
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I think they are supposed to be loose. The Saturn V instructions say not to glue the upper ring, because the contracting glue would dimple the airframe.

I haven't looked at my Skylab kit but I bet it's the same.
They are still way to loose. Besides if you follow the instructions on page 5 the top CR isn’t glued. After it’s inserted they want you to apply glue at the rear of the tube and then slide the last two CRs up to 3-3/8” from the bottom. Good luck with that. If you can get it all the way up before the yellow glue sets great. The bottom CR located just above th engine retainer has to be glued to the main tube with yellow glue. The instructions say nothing about glueing the top CR to the tube. The middle CR May or May not have glue on it once it’s positioned (if it’s positioned. So all the CRs are located in the main tube where there are no wraps to cover any dimpling.
If only the bottom CR is actually glued in place you are depending on one CR glue joint to hold an E or F engine mount in the main frame.
I’ll be modifying the construction and cutting the main tube at 210mm up from the rear and adding a coupler. This way I can insert an extra CR and have acces to glue things properly. I’ll be using Canopy glue which does not dimple the tubes. The main tube splice is located under one of the wraps so it will not show.
Will be working on making the coupler first as its 110 mm in perimeter and 200mm long made out of the lid of the box it came in. Middle CR will have to be relocated forward or a custom one made to fit the coupler.
 
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DigBaddy

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Drill some screws into one ring so you can put it in the back, but then be able to remove it. Epoxy an inner ring, then put the one with screws in place to ensure the tube is centered...but not epoxied. Once dry, pull off the ring with screws, or do another inner ring with epoxy. Then finish up with the one you put screws into and the top ring (there's four, correct?) Doing them this way allows you to work inside and get those inner ones secure. Epoxy won't shrink the tubing, and with all rings secured, you can put a decent motor in it without resorting to heavy plywood.
 
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Drill some screws into one ring so you can put it in the back, but then be able to remove it. Epoxy an inner ring, then put the one with screws in place to ensure the tube is centered...but not epoxied. Once dry, pull off the ring with screws, or do another inner ring with epoxy. Then finish up with the one you put screws into and the top ring (there's four, correct?) Doing them this way allows you to work inside and get those inner ones secure. Epoxy won't shrink the tubing, and with all rings secured, you can put a decent motor in it without resorting to heavy plywood.
Great idea! I think I’ll go that route using all new CRs. It will be a bit tricky getting the engine mount tube located at the right distance from the rear end of the main tube but not insurmountable. Thanks
 

DigBaddy

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Great idea! I think I’ll go that route using all new CRs. It will be a bit tricky getting the engine mount tube located at the right distance from the rear end of the main tube but not insurmountable. Thanks

You'll figure it out, and then you'll build a lot more rockets with that technique 😃
 

cls

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So, you're not going for scale points? G motors are too fast for that anyway. But yeah, big rocket flies better with more thrust. Gotta add nose weight. Then, a bigger motor. You know how this goes...
 

Back_at_it

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Yes. Way too loose.

Replaced the forward ring with one that I cut from hobby grade ply. Installed with BSI 30 min. epoxy. Much stronger and no issues with shrinking the tube.

I only send mine up on E20 and E30 motors.
 

JPalmer621

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Plenty of composite 24 mm motors out there too. I just fly my Saturn V on an F41. Great flight. I would reinforce the centering rings though
 
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Have changed out the three very loose CRs (5.39g each) supplied in the kit for four slightly heavier and tighter fitting ones (6.14-6.20g each). Used Bigdaddy’s suggestion and used screw eyes to help epoxy the two lower CRs inplace along with the engine retainer. Upper two CRs to be glued yet.
 

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I replaced the CRs on the transition between the 2nd and 3rd stages. They also were to small in diameter. Completed the transition wrap. I cut out the vac formed wraps and discovered that the tunnel location is incorrect on the top wrap. Will have to line it up properly and not on the line as stated in the instructions. Not to pleased with Estes on this kit.image.jpg image.jpg
 
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Installed the fins and fairings. I built up layers of cardboard to the correct hit to set the fins on and glue them to the main body tube using the alignment guide. Fins were glued on using testers plastic cement. Once dry I installed the fairings over the fins and glued them using Canopy glue on the fairing opening and card board base and Tamiya extra thin cement where the fairing meets the main tube.
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Completed the masking of the roll pattern. The task was more complicated because the wraps had changed and the the horizontal raised areas were no longe there. Had to arduously set the tape into each groove while maintaining a straight horizontal line.
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